Merge pull request #368 from aidancuckoo/patch-5

Update stm32f412zg_discovery.md

Author: makermelissa

_board/stm32f412zg_discovery.md

@@ -18,6 +18,11 @@ An embedded ST-LINK/V2-1 debugger/programmer is included; specialized add-on boa
 
 ## Purchase
 * [ST](https://www.st.com/en/evaluation-tools/32f412gdiscovery.html)
+* [Digi-Key](https://www.digikey.com/products/en?WT.z_cid=sp_497_0928_buynow&Enterprise=44&lang=en&Vendor=497&mpart=STM32F412G-DISCO)
+* [element14](https://nz.element14.com/stmicroelectronics/stm32f412g-disco/dev-board-arm-cortex-m4-mcu/dp/2664593?ost=STM32F412G-DISCO&CMP=GRHS-1000962&ddkey=https%3ASearch)
+* [Mouser](https://www.mouser.com/ProductDetail/STMicroelectronics/STM32F412G-DISCO?qs=%2Fha2pyFadujxcn39gZUbxVHiujvGbqjGwP%2F30QlZCd4Sdl12itu%2FNA%3D%3D)
+* [RS Components](https://nz.rs-online.com/web/p/processor-microcontroller-development-kits/1231065/?relevancy-data=636F3D3126696E3D4931384E53656172636847656E65726963266C753D656E266D6D3D6D61746368616C6C7061727469616C26706D3D5E5B5C707B4C7D5C707B4E647D2D2C2F255C2E5D2B2426706F3D31313326736E3D592673723D2673743D4B4559574F52445F53494E474C455F414C5048415F4E554D455249432673633D592677633D4E4F4E45267573743D53544D333246343132472D444953434F267374613D53544D333246343132472D444953434F26&searchHistory=%7B%22enabled%22%3Atrue%7D)
+* [Electronshik(site is in Russian)](https://www.electronshik.ru/item/ST/STM32F412G-DISCO)
 
 ## Contribute